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ridinpreacher's avatar
ridinpreacher
Explorer
Apr 28, 2018

Replacing Roof Top AC gasket/seal

Okay. I've finished the interior rebuild in our lance 835. You may have followed my posts previously as I sought out water intrusion found sealed. And now have replaced ceiling etc. Now ready to remove roof top a.c. and replace seal with a much higher quality recommended by Lance. While I have a.c. off, I plan to apply a roof coating on the aluminum roof. My question is. Will the adhesive on the new a.c. gasket seal to the roof coating. Or should I leave United where the a.c. gasket will cover.

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Truck Campers
  • AnEv942's avatar
    AnEv942
    Nomad
    Apr 30, 2018
    The only gaskets I've used only have adhesive on one side and that is placed against AC?
  • Joe417's avatar
    Joe417
    Explorer
    May 01, 2018
    It's been years since I had one with a metal roof, but I think I would clean it and leave it un-coated where the gasket seals.

    I've only ever had one that leaked. An 84 Coachman. Didn't cause any damage as it ran off the roofing and dripped into the floor out the inside vent and luckily caught it early. The weight of the AC caused the roof to sag around the opening just a small amount, allowing water to puddle slightly. Some are stronger than others and there is a bit of weight sitting up there and bouncing down the road.

    Before re-installing, I pulled the roofing staples and added 1/4 inch shims the width of the gasket around the AC opening underneath the roofing. That raised the surface just enough so that rain ran away from the AC gasket.

    I have made this modification since then to every camper we have had. It works very well and is something I think they should do at the factory. Even if the roof doesn't sag any.

    Also if you wanted to do this, if the AC has a support pad at the far end you'll need to add the same thickness shim there on top of the roofing. I used 3 or 4 layers of scrap EPDM roofing, stuck it down with Dicor sealer.

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